Add a PDF component extension

chrome/common/extensions/extension_constants.h

Index: chrome/common/extensions/extension_constants.h
diff --git a/chrome/common/extensions/extension_constants.h b/chrome/common/extensions/extension_constants.h
index 50920e8e35b11e82d8ccf8b7fc6b3ccb65d859f7..1f6543a782e59abe5e1faffe4ca0606f1dc65d28 100644
--- a/chrome/common/extensions/extension_constants.h
+++ b/chrome/common/extensions/extension_constants.h
@@ -109,6 +109,9 @@ namespace extension_misc {
   // The extension id of the Crosh component app for ChromeOS.
   extern const char kCroshBuiltinAppId[];
 
+  // The extension id of the PDF extension.
+  extern const char kPdfExtensionId[];
+
   // The extension id of the Office Viewer component extension.
   extern const char kQuickOfficeComponentExtensionId[];